A sufficiently advanced technological field is one where any expert would start laughing at you for suggesting "hardening" against bullets. The denominator for

A sufficiently advanced technological field is one where any expert would start laughing at you for suggesting "hardening" against bullets. The denominator for rockets is always mass. Most of the difficulty is derived from not just doing a thing, but doing it in as lightweight a way possible. There are rocket stages that won't even stand up under their own weight, we have to inflate them like balloons just to move them.